Friction-free infusion pump system

ABSTRACT

An infusion pump system for continuously injecting a medical substance contained in a supply chamber into a catheter connected to the body of the patient. The system includes a flattening means driven by a motor (10) and designed to flatten a portion (42) of the infusion tube and exert pressure in order to inject the medicinal substance into the catheter. The flattening means includes a rigid member such as a circular plate (32) of which the axis (34) has a geometrical position determined according to a hub (12) driven by the motor (10) in such a way that said axis (34) of the plate intersects the axis (14) of the hub at a fixed point (X). The plate (32) has projections (38, 40) which flatten the catheter (42) as the motor (10) rotates. A fork (43) held by a ball (44) prevents the plate (32) from rotating relative to the catheter. Friction on the walls of the catheter (42) is thus avoided and high infusion accuracy may be achieved.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an infusion pump system of the typecomprising an electrical motor and a pump, for continuously injecting amedicinal substance contained in a supply chamber into a catheterconnected to a patient's body, thanks to an infusion tube connected tothe pump, said pump comprising flattening means driven by the motor forflattening a portion of the infusion tube so as to exert a pressure andinject the medicinal substance into the catheter.

2. Description of Prior Art

More and more human diseases are treated by injecting a medicinalsubstance into the patient's body. As an example, in the treatment fordiabetes, it is necessary to perform at regular time intervals insulininjections to the patient. Other diseases like cancer are also treatedthru injecting of medicinal substances. But frequent injections usingneedle and syringe are a problem with respect to the regularity of theinjections to be performed, and even more, the skin damages incurredafter multiple performed injections.

The solution has then been for the patient to follow a continuoustreatment thanks to an infusion needle fixed at the input of thecatheter connected to the patient, in general with an implanted chamber,connected to a pump.

The improvement brought about by this technique has been that thepatient carries the pump along, in a pocket, or hanging from a belt. Thepump driven by a small electrical motor, continuously injects themedicinal substance in the catheter and thus provides the necessarychimiotherapy, without having to always perform continuous injectionsthru needle and syringe.

There is currently available on the market several pump types aimed atcontinuous infusion of medicinal substance. The first type comprisespumps having rollers. In those pumps, rollers are generally placed atthe periphery of a cylinder rotated by the electrical motor. The rollersin turn flatten a portion of the infusion tube. The system is soarranged that two or more rollers are simultaneously in contact with theinfusion tube. Thus a first roller flattens the infusion tube more andmore and prevents any flow within, while at the same time a secondroller downstream, frees the portion of the tube previously flattenedand thus induces a flow in the infusion tube, due to the pressureexerted by the flattening with the first roller. One can refer todocuments EP-19816, EP-19817 and EP-197179 which deal with that sametype of pump.

Pumps with rollers, although very simple, have the drawback of featuringrotating elements for exerting the flattening on the infusion tube.Inevitably, frictions occur between the rollers and the infusion tube,which leads to internal constraints within the walls of the infusiontube and consequently a permanent deformation of said walls. Consequenceof the walls deformation is that metering precision for the medicinalsubstance to inject is impacted. Thus pumps with rollers have anaccuracy of about 10 to 15%. Such a low accuracy is not acceptable forsubstances requiring a high injection precision.

A second type of pumps is of the type with fingers. In such a pump,several fingers flatten the infusion tube in different places andintermittently. When at least one finger flattens the infusion tube inone place, thus blocking any upstream flow in the infusion tube, atleast one other finger releases downstream from the pressure it exertedon the infusion tube, and therefore enables the downstream flow of themedicinal substance, started with the flattening finger.

Pumps with fingers do not have the drawback of frictions occurring withthe infusion tube walls since there is no rotating element moving alongthe infusion tube. Those pumps are therefore more precise than the pumpswith rollers. An accuracy higher than 5% can be reached with pumps withfingers. Unfortunately the latter pumps require a mechanical driving ofthe fingers involving a rather complex system of cams. To still increasethe accuracy of this type of pump, the number of fingers has beenincreased, along with the complexity of the implementing mechanics. Thusthe pump described in document U.S. Pat. No. 4,671,792 has sevenfingers. The complexity renders it impossible to realize a miniaturizedpump with fingers. Another drawback, not the least of them, is that thecomplexity of the fingers driving system is accompanied with a highpower consumption and thus a frequent replacing of the electrical motorbatteries.

A third type of pump being also used for infusions is described inpatents U.S. Pat. No. 2,818,815 and EP-A-103.073. This type of pumpfeatures a rigid part under the form of a disc coupled to the drivingshaft of the pump motor and having an axis at a certain angle with saidshaft, also called nutation angle. When the motor rotates, it drives thedisc in an oscillatory motion such that the external rim of the discflattens the infusion tube placed as a ring in a plan perpendicular tothe motor driving shaft.

Pumps of the type above partly solve the above-mentioned drawbacks inthat they do not have rotating elements such as the ones in pumps withrollers, or complex elements such as the ones required in the pumps withfingers. However, although it is mentioned in the above-referenceddocuments that the disc moved in an oscillatory motion does not rotate,nothing in there prevents it from rotating and thus exerting a frictionon the infusion tube at the same time it flattens it. Besides, pumps asdescribed in the prior art do not allow an accurate control of theinjected substance flow.

SUMMARY OF THE INVENTION

The goal of the invention is therefore to solve the above-mentionedproblems and propose a pump system for performing continuous infusion,with a high accuracy, which can be easily miniaturized and low energyconsuming.

Another goal of the invention is to realize an infusion pump systemhaving no rotating element for flattening the infusion tube so as toavoid frictions with said tube, and no complex mechanical elements, soas to be easily miniaturized and limit the power consumption.

Still another goal of the invention is to propose an infusion pumpsystem of the type with rigid oscillating element as described indocument U.S. Pat. No. 2,818,815, but which oscillating element isprevented from rotating while it is oscillating.

Yet another goal of the invention is to propose an infusion pump systemof the type as described above in which the oscillating element hasprojections allowing an accurate metering of the medicinal substanceflow.

The object of the invention is therefore an infusion pump systemcomprising an electrical motor and a pump designed for continuouslyinjecting a medicinal substance contained in a supply chamber into acatheter connected to the body of a patient thru an infusion tubeconnected to the pump, further comprising flattening means driven by themotor for flattening a portion of the infusion tube and exert pressurein order to inject the medicinal substance into the catheter, thisportion of the infusion tube being arranged in a predetermined curveshape within a plan, and the flattening means comprising a rigidoscillating element, of which the external rim corresponds to saidpredetermined curve shape and the geometrical position relative to themotor axis is such that the axis of the rigid element intersects themotor driving axis at a predetermined angle, the rigid element beingarranged relative to the perpendicular plan so that its external rimflatten a different portion of the second part of the infusion tubewhile the motor is rotating, which results in injecting the medicinalsubstance in the infusion tube.

The oscillating element comprises blocking means in the shape of a forkheld by a fixed element preventing any rotating motion of the rigidelement relative to the plan perpendicular to the driving axis, so as toavoid any friction of the rigid element on the portion of the infusiontube being flattened.

BRIEF DESCRIPTION

The invention will be better understood from the following detaileddescription read in conjunction with the following schematics:

FIG. 1 is a rough sketch illustrating the principle of the pump systemaccording to the invention;

FIG. 2 represents a cross sectional view of an embodiment of the pumpsystem according to the invention;

FIG. 3 is a vertical cross sectional view of the circular plate used asflattening means in the embodiment of the pump system of FIG. 2;

FIG. 4 is a cross sectional view of another embodiment of the pumpsystem according to the invention;

FIG. 5 is a top view providing a rough sketch of the portion of theinfusion tube flattened by an oscillating element with 6 projections andthe placing of the projections relative to the infusion tube;

FIG. 6 is a top view providing a rough sketch of the portion of theinfusion tube flattened by an oscillating element with 12 projectionsand the placing of the projections relative to the infusion tube;

FIG. 7a is a bottom view of the oscillating element with 12 projectionsof FIG. 6;

FIG. 7b is a cross sectional view of the oscillating element with 12projections of FIG. 7a; and

FIGS. 8a and 8b provide a rough sketch of an oscillating element with 6numbered projections and the graph versus time of the flow of injectedmedicinal substance when using such an oscillating element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principle of the invention is illustrated in figure 1. An electricalmotor 10 rotates a hub 12 thru a shaft 14. A rigid disc 16, preferablymade of metal, is connected to the hub 12 by its axis 18 at an eccentricpoint on the bottom part of hub 12, said point being preferably at halfthe radius of the hub. The axis 18 is in a geometrical position fixedwith respect to hub 12 but is free to rotate around itself. Axis 18presents a nutation angle PHI comprised between 3 and 8 degrees with thehub axis 20 so that disc 18 present the same angle with a planperpendicular to the hub axis. The latter plan is represented on thefigure as being horizontal. Axis 18 intersects with axis 20 at a point Xthe position of which is precised below.

Rotated by motor 10, the hub 12 drives the disc 16 in a rotating motionaround axis 20 so that its lower point describe a circle 22 in the planperpendicular to the hub axis. This is obtained by having axis 18 of thedisc 16 intersecting the axis 20 of the hub 12 (which besides results inthe axis 18 describing a cone with and axis 20 and a summit X). Theintersection point X is preferably in the plan of circle 22. Infact, thecharacteristic stated above is still true if the intersection point X isnot in the plan of circle 22 but slightly above or underneath it.

The characteristic obtained thru the structure roughly sketched in FIG.1, according to which the lower point A of disc 16 describes a circle 22can be exploited as follows. If, in place of circle 22, a tube is placedor any other element that can be flattened, this tube or element will beflattened by disc 16 at point A. This flattening of the tube will befriction-free from the side of disc 16 under the condition that disc 16is prevented from rotating around its axis 18 when the latter isdescribing a cone of summit X, while the whole system is driven by motor10. This characteristic can be used to flatten a tube connected on oneside to an infusion liquid supply chamber, and on the other side to acatheter connected to a patient, so as to continuously inject theinfusion liquid within the catheter.

The practical implementation of a pump system based on the principleillustrated in FIG. 1, will now be described with respect to FIG. 2.FIG. 2 is a cross sectional view of a preferred embodiment of pumpsystem according to the invention. As already illustrated in FIG. 1,motor 10 is connected to hub 12 thru the shaft 14. The shaft 14 is fixedin the hub 12 by a bolt or screw 30 or any other appropriate means.

A circular plate 32 (corresponding to the disc 16 in FIG. 1) is kept ina predetermined geometrical position with respect to hub 12 thanks to ashaft 34 lodged in a cavity 35 of the hub 12, but free to rotate arounditself. Shaft 34 is prevented from detaching from hub 12 thanks to ajoint 36 fitting in a groove placed at the bottom of cavity 35 aimed atreceiving shaft 34. As will be seen further in the description, thecircular plate 32 features projections 38, 40. As explained with respectto FIG. 1, the circular plate corresponding to disc 16 in FIG. 1 is inmotion, when the motor rotates hub 12, in an oscillating motion suchthat the axis of shaft 34 which intersects the axis of shaft 14 in afixed point X, describe a cone of summit X. During this motion, thecircular plate 32 has a lower point, which describes a circle located ina plan perpendicular to the axis of shaft 14. In the preferredembodiment of FIG. 2, the lower point coincides with the external faceof one projection which changes throughout the motion. The external faceof the projection, when the latter is in low position, flattens then theinfusion tube a portion of which is located at the circle described bythe lower point of circular plate 32. Thus, as illustrated in FIG. 2,projection 40 when in low position flattens the infusion tube 42 placedin a groove of supporting stand 45. As the circular plate features aplurality of projections, other projections are in the position forflattening the infusion tube, some of them downstream with respect toprojection 40 and being at the initial flattening phase while othersupstream with respect to projection 40 are already in the releasingphase of infusion tube, all this resulting in the medicinal substanceflowing down the infusion tube.

As has been assigned in the goals of the invention, the system asillustrated in FIG. 2 is designed to be frictionfree with respect to theinfusion tube. To achieve that, it is necessary that the circular plate32 be prevented from rotating around its axis. This preventing isobtained with a fork 43 rigidly locked with the circular plate, which iscontinuously engaged with a ball (44) but without being interlocked withit. When motor 10 rotates the hub 12, the shaft 34 rotating freely incavity 35 of the hub 12 does not have a rotating motion relative to thehorizontal plan in which the infusion tube is located, since the fork 43held by the ball 44 prevents the circular plate 32 from rotating. On thecontrary, shaft 34 has a rotating motion relative to the hub as areference. A lubricating coat such as `Teflon` needs then be depositedon the portion of shaft 34 inserted in hub 12, or on the walls of cavity35.

FIG. 3 represents the circular plate 32 in a vertical cross sectionalview. This circular plate features 6 projections, of which 4 can beseen, projections 38 and 40 being illustrated on FIG. 2, the projections46 and 48, and two other projections hidden by the projections 46 and48. Is also illustrated on the figure, the fork 43 which prevents thecircular plate 32 from rotating around itself. The end surfaces of theseprojections can be at an angle with respect to the middle plan of thecircular plate so as to be essentially parallel to the plan of theinfusion tube, when a given projection is in the lower position andflattens the infusion tube. These end surfaces can also be rounded so asto not damage the infusion tube.

A second embodiment is represented in cross section on FIG. 4. Asillustrated, shaft 34 of the circular plate 32 is mounted within the hub12, of which only a portion has been represented, thanks to a ball andsocket joint. A ball 50 interdependent with the shaft 34 can move freelywithin a socket 52 of the hub 12. In the same fashion, the other end ofthe shaft 34 is interdependent with a ball 52 which can move freely in acavity 53 of a fixed stand 54. The circular plate 32 is blocked by a nut56 on one hand, and maintained adjacent said nut by a spring 58 on theother hand. In the same fashion as in the embodiment represented withFIG. 2, the circular plate 32 features projections among which theprojections 60 and 62, the projection 62 being represented when in itsposition of flattening the infusion tube 64. The latter is receivedwithin a groove 66 of a supporting stand 68.

The number of projections can vary as will be seen hereafter. Butwhatever this number, the projections must be distributed around thecircular plate so that none of the projections reside above the locationinbetween input and output of the infusion tube where obviously there isno tube potion to flatten. Thus, it can be seen either on FIG. 5representing the ring portion of the infusion tube between its input 70and its output 72 in the case of 6 projections, or on FIG. 6representing the same infusion tube in the case of a circular plate with12 projections, that none of the projections resides above the locationwith no infusion tube between the input 70 and the output 72.

The higher number of projections in the circular plate, the higheraccuracy is obtained with regulating the flow of medicinal substance.Indeed, the projections allow injecting the liquid in the infusion tubein discrete quantities under the condition that there always be oneprojection flattening the infusion tube. If, at a given time, noprojection is in lower position, there is a risk of upstream backing ofthe substance along the infusion tube. It is thus necessary that when aprojection is about to release its flattening, there is anotherprojection about to reach the lower position. Under this condition, theliquid is driven within the infusion line with a higher accuracy whenthere is more projections to the circular plate.

Besides, the projections induce pressure peaks within the infusion tubewhich allow avoiding the development of blood clots at the far-end tipof the infusion tube. As represented in FIGS. 5 and 6, the aggregatesurface of the projections is approximately half the aggregate surfaceof the circular plate. Although this percentage of 50% is preferable, itis possible to increase or even decrease it without departing from thescope of the present invention. With a percentage of 50%, the volume ofliquid moved at each revolution, is about 50% of the total volume withinthe infusion tube in the ring. FIG. 7a is a bottom view of the circularplate 32 in the embodiment with 12 projections as illustrated in FIG. 6.FIG. 7b is a cross sectional view of the circular plate as illustratedon FIG. 7a following plan A, showing the fork 43 preventing the circularplate from rotating around itself.

The number of projections is also related to the nutation angle. A widenutation angle (approximately 8 degrees) obviously requires projectionsclose to each other, and therefore a large number of projections toavoid any upstream backing problems. On the contrary, if the nutationangle is narrow (approximately 3 degrees), a large number of projectionsis not necessary. It is to be noted that the above reasoning isapplicable whatever the circular plate dimensions; however, the optimumnutation angle for a given number of projections varies according to thecircular plate diameter.

FIGS. 8a and 8b illustrate the pump with a circular plate having 6projections as in FIG. 5. On FIG. 8a, the projections have been numberedfollowing the rotation direction of the pump indicated with an arrow.That means that the infusion tube further to the input 70 is flattenedfirstly by projection 1, then projection 2, and so on, so as to move theliquid towards the output 72 of the infusion tube. The flow D of liquidinjected in the infusion tube from output 72 can then be represented aspulses function of time as in FIG. 8b. This comes from the fact that theinjecting of liquid in the infusion tube is maximum when projections 1to 5 are in lower position, and minimum when projection 6 gets to thelower position as illustrated in the following correspondence tablebetween the instants T of FIG. 8 and the numbers of projections whichare in the lower position: ##STR1##

Although the circular plate as illustrated in the embodiments of FIGS. 2to 8 features projections designed for flattening the infusion tube, itwill be obvious to the man skilled in the art that other shapes couldalso be used. Thus, it is possible to design the external face of thecircular plate to have a sinusoidal profile. The external face of thecircular plate can be truncated or even plan as of the disc on FIG. 1,although the latter shape does not seem to lead to the better results.

In the embodiments illustrated on the figures, the portion of theinfusion tube that can be flattened is a circle or a ring. However it ispossible to lay the infusion tube on a plan following a curve shapedifferent from the circle, with a disc having an external rimcorresponding to this curve shape.

I claim:
 1. Infusion pump system comprising an electrical motor (10) anda pump driven by said motor, designed for continuously injecting amedicinal substance contained in a supply chamber into a catheterconnected to a patient's body thru an infusion tube (42) connected tothe pump, said pump comprising flattening means driven by an axis (18)having with the driving shaft (14) axis of said motor a predeterminedangle, said flattening means including a rigid oscillating element (16)of which an external rim thereof faces a portion of said infusion tubearranged in a predetermined curve shape (22) in a plane perpendicular tosaid driving shaft (14) axis, for flattening said portion of theinfusion tube so as to exert a pressure and inject the medicinalsubstance into the catheter while the motor is rotating;said systembeing characterized in that said rigid oscillating element comprisesblocking means (43) in the shape of a fork held by a fixed element (44)preventing any rotating motion of said rigid element relative to theplane perpendicular to said driving shaft axis, so as to avoid anyfriction of said rigid element on said portion of the infusion tube. 2.The system according to claim 1, characterized in that said rigidelement (16) is of a shape essentially circular and said portion of theinfusion tube is arranged following the arc of a circle (22) in saidplane perpendicular to the driving shaft axis.
 3. The system accordingto claim 2, characterized in that said external rim the shape of thecircular plate (32) includes projections (38, 40) which sequentiallyflatten said portion of the infusion tube in the shape of an arc of acircle.
 4. The system according to claim 2 or 3, characterized in thatthe axis (18) of said rigid element (16) intersects with the drivingshaft (14) axis at a point (X) located in said plane perpendicular tosaid driving shaft axis.
 5. The system according to any of the claims 1characterized in that said motor (10) rotates a hub (12), and said rigidelement carries a shaft (34) mounted free in a cavity of said hub so asto be able to rotate around its axis within said cavity when the hub isdriven by the motor.
 6. The system according to any of the characterizedin that said motor (10) rotates a hub (12), and said rigid elementcarries a shaft (34) mounted free in said hub with a ball (50) so as tobe able to rotate around its axis when said hub is driven by said motor.